What is the amplification of a preamp?  What range?  Can I build a preamp with, say, a 4558 type chip?  Or does that not give enough juice?  Say I build a booster with a gain of 500.  Is that enough?  And I know that there are schematics out there, but I was just looking for some numbers -- raw data.  Thanks for the info!!
-Joe Hart

Preamps do a couple of things... they boost the signal level, but perhaps more importantly they increse the current and lower the impedance.

You don't need much gain or else you run out of headroom and get clipping fairly quickly. A gain of 10-20 will bring a guitar up to line level, giving any additional processing plenty to work with. A 4558 will work fine, but for strictly preamp purposes, I would suggest a low noise opamp like a 5534 (or 5532). Those chips have great output drive.

Take care,
-Peter